The proposed research initiates investigations into the mechanisms of hearing loss, with particular emphasis on the processes involved in hearing loss caused by exposure to noise and by chemical toxins. In addition, a major portion of the research is concerned with the identification of auditory and vestibular deficits associated with specific etiologies of hearing loss, in order to provide a better basis for differential diagnosis of auditory disorders. Data obtained from research techniques in electron microscopy, psychoacoustics, biochemistry, neurophysiology, vestibular physiology, light microscopy, histochemistry, and immunology, as well as those in clinical medicine, will provide the basis for accomplishment of the primary goals of this research program, namely: the understanding of the mechanisms of hearing loss and the improvement of methods of management of patients with hearing loss.